This invention relates to a tenter frame for treating web materials such as knitted fabrics, woven fabrics, felted fabrics, or the like, to apparatus for use in conjunction with a tenter frame, and to methods for use of same. More particularly, the present invention is directed to a tenter frame equipped with improved means for removing a web being processed on the tenter without loss of control over the web, to the removal means per se and to improved methods of removal of webs from tenters.
In the general operation of tenter frames, a web material enters the machine at one end where the web is engaged along its edges or selvages by a series of upwardly extending pins which penetrate the web material. The pins are, in turn, secured to and supported by two endless tenter chains. The web material is thus held along its opposite edges by the upwardly extending pins for the full period of web travel through the tenter frame where it may be subjected to various and sundry treatments. For example, where the web material is a knitted or woven fabric, it may simply be washed, shrunk or stretched as desired and maintained in a desired dimensional state by the tenter chains as it dryed. In any event as web material moves through the tenter frame and reaches the exit end it becomes necessary to remove the web from the pins on the tenter chains for ultimate removal of the web from the tenter. At the same time in processing many web materials, it is necessary to trim the edges or selvages of the web material to remove the portion which has been penetrated by the pins on the tenter chains. Otherwise a defect may be created in the web. Other webs, however, are unaffected by the pin holes and no trimming is necessary.
One prior art arrangement for web removal from a tenter frame is illustrated in FIG. 1. In FIG. 1, a tenter frame generally 10 is shown schematically, including a portion of a tenter chain 12 with a plurality of upward extending tenter pins 14. In tenters of this type, the frame is provided with a pair of tenter chains but only one is illustrated in FIG. 1 for purposes of clarity. A fabric F is pinned by pins 14 along opposite selvages and the chains are moved inwardly or outwardly with respect to each other to achieve a predetermined fabric width. At an exit end of tenter 10, fabric F is entrained about a pinned take-off roll 16 which is spaced from tenter pins 14 and is intended to engage (pin) the edges of the web material before it is disengaged from tenter pins 14. Fabric F is then entrained about a second pinned cutter support-roll 20 spaced from roll 16 where the edge is trimmed from the fabric by a cutter blade 18, with the selvage S being separated from the fabric F as illustrated, as by way of suction.
One problem with the arrangement of FIG. 1 follows. Web entering tenter frames sometimes escapes becoming pinned along short portions of same. At such unpinned areas, the web which is under tension necks in towards the center of the tenter and away from the pins. Consequently, at the exit end of the tenter, the necked-in portion of the web may not make contact with pins on roll 16, or roll 20. Consequently, once the previously removed selvage is cut by element 18, a new trimmed end is produced which is not removed by suction or the like, leaving the remainder of web F on the tenter pins which continues to build up around roll 20 and eventually disrupts tenter operation, not to mention defects produced in web F. Also, control of web F is lost in the space between rolls 16 and 20.
A second prior art arrangement is illustrated in FIG. 2 of the drawing. A single pin-cutter support roll 20 functions as the guide roll for pinning web F before it is disengaged from the tenter pins 14. Selvage S is trimmed from the web F by a cutter 18 which operates in conjunction with pinned roll 20. Again, the same problems as noted above are present, in that portions of web F are free of pins 14 before being picked up by pinned roll 20 and define necked-in portions, wherefore control over web F is lost. In this arrangement, cutter 18 would also create a new leading edge at the necked-in portion and the trimmed web would build up around roll 20. Prior art arrangements of FIGS. 1 and 2 are generally typical of the known prior art in that both fail to exert positive control over the web material before its removal from the tenter chain pins.
The present invention overcomes the problems noted above. Particularly, prior to disengagement from tenter pins 14, the web is pinned by a pinned removal roll. Removal pinning occurs inside the conveyor pin line and thus minimizes missing of small web sections. Also even if a small section is missed, apparatus according to the present invention automatically releases the pinned waste which will permit a new leading edge of waste to be removed. Consequently, the web waste will not continue around any roll or conveyor and create problems for the tenter.
In addition to the above, the present invention permits accurate web trimming. Such results in substantial savings over conventional methods. Though web widths of only one-quarter inch or so may be involved, significant amounts of web can be wasted during continuous running of a tenter. The present invention thus represents significant improvement over known prior art.